The present invention relates to basic magnesium-zirconium complexes useful as antiperspirants. More particularly the invention is directed to the production of highly effective antiperspirant systems using zirconium as the primary astringent ingredient and magnesium as a buffering agent as well as a source of synergistic antiperspirant action when reacted with zirconium.
It has been known in the art for some time that zirconium salts provide exceptionally effective antiperspirant properties. Such zirconium compounds have included particularly the acidic zirconium salts, such as zirconium oxy chloride or zirconyl chloride, zirconium hydroxy chloride, and other halide and sulfate substitutes of the salts. However, the zirconium salts are extremely acidic and irritating to the skin. For example, a solution of zirconyl chloride which is effective as an antiperspirant has a pH of only about 0.8 and a solution of zirconyl hydroxy chloride which is effective as an antiperspirant has a pH of only about 1.2. As a result, it is necessary to buffer these solutions up to a pH which is suitable for application to the human skin, i.e., up to at least about 3 to 5.
A number of prior attempts have been made in the art to buffer solutions of zirconium salts or to form zirconium complexes which take advantage of the effectiveness of zirconium compounds. One early attempt included the development of sodium zirconium lactate for use in cologne-stick type formulations. This lactate complex salt was sufficiently alkaline (pH 8.5), but was ineffective as an antiperspirant, and was repeatedly implicated in the generation of "zirconium granulomas" in some users.
Other attempts to make use of the acidic zirconium salts involved the buffering of solutions of these salts with urea (see U.S. Pat. No. 2,814,584 to Daley) or water soluble amino acids (see U.S. Pat. Nos. 2,814,585 to Daley and 2,854,382 to Grad) or aluminum hydroxy halides (see U.S. Pat. No. 2,906,668 to Beekman).
More recently, various derivatives have been formed incorporating zirconium compounds, including the amine-amide derivatives of U.S. Pat. No. 3,407,254 to Siegal et al., and the polyhydroxy derivatives of U.S. Pat. No. 3,405,153 to Jones and Rubino.
In addition, Rubino copending application Ser. No. 418,712, filed Nov. 23, 1973, entitled "Aluminum-Zirconium Anti-Perspirant Systems With Salts Of Amino Acids", and other related copending applications describe other systems in which amino acids have been incorporated in aluminum-zirconium complexes to offset the acidity of the zirconium and aluminum as well as provide other advantages to the antiperspirant. Nevertheless, still more efficient and advantageous methods are being sought to combat the acidity of zirconium while at the same time maintaining or improving antiperspirant efficacy.
Various double salts, co-precipitates, and complexes of magnesium and aluminum have heretofore been described in the patent art and technical literature. For example, in U.S. Pat. No. 2,797,978 the preparation of hydrous gels comprising aluminum magnesium hydroxy carbonate is described including its intended use in oral administration as an antacid for treatment of peptic ulcer and other symptoms of gastric hyperacidity. Numerous other patents describe gels and gelatinous precipitates comprising magnesium and aluminum in various proportions for similar use as antacids.
It has also been proposed in U.S. Pat. No. 2,350,047, to incorporate into antiperspirant solutions or creams containing certain astringent aluminum salts, small amounts (from about 1 to 3 percent) of a water insoluble base, such as an oxide, hydroxide or carbonate of zinc, aluminum or magnesium, to reduce the deteriorating effect of these aluminum compounds upon fabrics, particularly when such fabrics are exposed to hot ironing. The incorporation of larger proportions of these basic compounds is contraindicated in the patent and is stated to reduce the perspiration inhibiting effect of the astringent salt.
In accordance with U.S. Pat. No. 2,571,030, the corrosive effects on fabrics of antiperspirant cream compositions containing aluminum chlorohydroxide or aluminum chloride, can be reduced by forming a water-dispersible double complex of the aluminum chloride with calcium chloride or with chlorides of other bivalent or monovalent metals. Examples of such other metal chlorides suggested in the patent, are those of the alkali metals, of zinc and of magnesium. Such added metal halides are advocated to be employed in the proportion of 0.2 to 15 parts by weight to 100 parts of aluminum, each being calculated as the element (corresponding to a maximum of less than 7 parts CaO or MgO per 100 parts of Al.sub.2 O.sub.3).